The present invention relates to the field of gas turbine combustion systems used for generating electrical power, and more particularly, this invention relates to a gas turbine combustor integrated with the nozzle of the turbine, such as the first stage nozzle.
The combustion systems used in current dry, low NOx (DLN), gas turbine combustion systems are large, complex and expensive. As disclosed in commonly assigned U.S. Pat. No. 6,217,280 to Little and published application no. 2001/0032450 to Little, the disclosures which are hereby incorporated by reference, a gas turbine combustion system of conventional construction is illustrated and generates electrical power by techniques well known to those skilled in the art.
This complicated type of assembly includes a main combustion turbine having a compressor assembly, a combustor assembly with a transition section or alternately an annular combustor, and a first turbine assembly. A flow path extends through the compressor, combustor assembly, transition section, and first turbine assembly, which is mechanically coupled to the compressor assembly by a central shaft. An outer casing creates a compressed air plenum, which encloses a plurality of combustor assemblies and transition sections that are disposed circumferentiality about the central shaft.
This type of gas turbine combustion system operates as a dry, low NOx (DLN) system having low part per million (ppm) NOx emissions. This low ppm NOx emission is necessary to maintain strict environmental standards during operation. As a result, these gas turbine combustion systems are complicated and can be expensive to maintain. It would be desirable if the size and complexity of the gas turbine combustion system could be reduced, allowing a shorter gas turbine with fewer parts without sacrificing the dry low NOx capabilities of current gas turbine combustion systems.
The present invention provides a reduced size and lower complexity gas turbine combustion system that permits a shorter gas turbine with fewer parts without sacrificing the dry low NOx capability of current gas turbine power generation systems. The cost reduction for a manufacturer and subsequent savings can be passed on to the industry to reduce the cost of electricity over the life cycle of a power plant in which the gas turbine is installed.
In accordance with one aspect of the present invention, a gas turbine combustion system used for generating electrical power includes a compressor that receives and compresses air. A first stage turbine nozzle is flow connected to the compressor and receives a portion of the compressed air from the compressor within a first air flow. A torus configured combustion chamber is positioned around the first stage turbine nozzle and receives a portion of the compressed air from the compressor within a second air flow that is passed through the combustion chamber where air and fuel are mixed and combusted. This combusted mixture is discharged into the first stage turbine nozzle to mix with the first air flow through the first stage turbine nozzle while achieving a dry low NOx combustion.
The first air flow has a velocity through the first stage turbine nozzle for generating sufficient aerodynamic pressures between the first and second air flows to accomplish an adequate air flow split between first and second air flows. The combustion chamber is configured for producing a radially inward flow of air that is discharged into the first stage turbine nozzle to mix with the first flow. In one aspect of the present invention, the fuel-to-air ratio within the combustion chamber is maintained below stoichiometric. The fuel-to-air ratio could be between about 0.18 to about 0.36.
In yet another aspect of the present invention, the combustion chamber includes a backside cooling surface over which compressed air from the compressor is passed to aid in cooling the combustion chamber. A catalytic surface is positioned within the combustion chamber and contacts the air and fuel mixture to initiate and maintain a catalytic reaction of fuel. The combustion chamber further comprises interior walls in which the catalytic surface is positioned. In yet another aspect of the present invention, the combustion chamber further comprises a backside cooling surface over which compressed air is passed to aid in cooling the catalytic surface.
In yet another aspect of the present invention, air is deflected off a compressor exit diffuser into a second air flow that is passed through the combustion chamber where air and fuel are mixed and combusted, and discharged into the first stage turbine nozzle to mix with a first air flow. It is also passed over the backside cooling surface for cooling the combustion chamber.
A method of operating a gas turbine for generating electrical power is disclosed and comprises the step of splitting a compressed air flow from a compressor into a first air flow that passes the compressed air through a first stage turbine nozzle. The compressed air is also split into a second air flow that is passed through a torus configured combustion chamber positioned around the first stage turbine nozzle such that fuel and air are mixed and combusted. The two air flows are mixed at the first stage turbine nozzle, while achieving a dry low NOx combustion.